1. Field of the Invention
The present invention relates to the lamination of metal foils to polyimide films.
2. Description of the Prior Art
Polyimide films having an adherent metal foil layer have been described in the literature. Such laminates are useful as components for electrical circuitry.
U.S. Pat. No. 3,717,543 to J. R. Sinclair et al. describes the use of an epoxy resin-containing adhesive to bond polyimide films and metal foils. The Sinclair patent specifies that the adhesive contain at least 50% by weight of an ammoniated acrylic copolymer, e.g. of the methyl methacrylate-glycidyl methacrylate type.
U.S. Pat. No. 3,904,813 to G. L. Groff also describes the use of an adhesive composition containing epoxy resin to bond polyimide film and metal foil. The adhesive that is described in the Groff patent contains 100 parts by weight of a completely reacted adduct of a carboxyl-terminated polymer and an epoxy compound. Additionally, the adhesive contains between about 25 and 200 parts by weight of an epoxy resin and sufficient epoxy curing agent.
Neither of the above patents describes adhesive compositions containing a predominant amount of epoxy resin without the large amounts of polymeric modifier used in the Sinclair et al. and Groff technology.